GHC Devs,
The wiki page for Phase I of Dependent Haskell describes an approach to constrained type families:
https://ghc.haskell.org/trac/ghc/wiki/DependentHaskell/Phase1#Typefamilyequationscanbeconstrained
Did that land in GHC 8.0 and, if so, is the updated syntax documented somewhere?
V/r,
-Evan